The present disclosure relates generally to preventing loops in a computer network, and more particularly, mechanisms for preventing loops in networks operating different protocol to provide a loop-free topology.
Link state routing is a protocol that allows a node in a network to determine network topology by sharing information about transmission cost to each of its neighboring nodes. Link state routing packets are transmitted to neighbors and received from neighbors. The least expensive path to various destinations is determined using the link state information. Transient loops can sometimes arise when network topology changes because neighboring nodes may not be forwarding transmissions using the same generated network topology. One mechanism for preventing loops is Spanning Tree Protocol (STP).
The Spanning Tree Protocol executes on a switch and operates to maintain a loop-free topology in a Layer 2 (L2) switched network. Devices such as a Classical Ethernet (CE) switches may use STP to prevent loops. Other devices such as Data Center Ethernet (DCE) switches may be configured to use protocols other than STP to provide loop-free operation.
While STP and other protocols work well for a stand-alone network comprising switches that utilize only one protocol for preventing loops, the different protocols may not inter-operate and therefore cannot be used in a combined network operating with different protocols.
In addition to preventing loops in a combined network, it is also desired to provide rapid convergence in accordance with Rapid Spanning Tree Protocol (RSTP) (IEEE 802.1w) regardless of the protocols used in the networks for preventing loops.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.